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Interpretive Summary: Grapes are rich in many compounds that have significant benefits to human nutrition and health. Polyphenols are one class of such compounds. In this study, we evaluated the polyphenolic profiles in the ripe berry samples of 344 European grape (Vitis vinifera) cultivars for two consecutive years. These cultivars represent a diverse collection of Vitis vinifera germplasm maintained at the USDA-ARS Vitis Clonal Repository in Davis of California. A total of 36 polyphenolic compounds, including 16 anthocyanins, 6 flavonols and 6 flavanols, 6 hydroxycinnamic acids, and 2 hydroxybenzoic acids, were identified and quantified by using HPLC instruments. Significant variation was found in the grape germplasm for these compounds. In general, wine grapes had higher concentrations than table grapes for most of these compounds. Berry colors affected the total contents of anthocyanins, but had no apparent impacts on other groups of compounds. The relative abundances of these five groups of compounds are in the order of anthocyanins, flavanols, flavonols, hydroxycinnamic acids, and hydroxybenzoic acids which explained 52.1%, 23.3%, 5%, 17.6% and 2% of the total phenolic variation, respectively. Positive correlations (0.151-0.535) were found among these groups of compounds. As expected, these groups of compounds were all negatively correlated with berry weight. From these analyses, several cultivars with high contents of total and individual polyphenols were identified and could be used for development of new grape varieties.

Technical Abstract: Polyphenols are an important class of secondary metabolites with significant benefits to human nutrition and health. As a part of our effort to assess grape germplasm for its potential health and nutrition value, we evaluated the polyphenolic profiles in the ripe berry samples of 344 European grape (Vitis vinifera) cultivars for two consecutive years. These cultivars represent a diverse collection of Vitis vinifera germplasm maintained at the United Sates Department of Agriculture-Agricultural Research Service Vitis Clonal Repository in Davis of California, USA. A total of 36 polyphenolic compounds, including 16 anthocyanins, 6 flavonols and 6 flavanols, 6 hydroxycinnamic acids, and 2 hydroxybenzoic acids, were identified via HPLC-MS and quantified by HPLC-DAD. The total content of anthocyanins ranged from 0 to 5.123 mg g-1 FW with malvidin 3-O-glucoside and malvidin 3-O-(6-O-coumaryl)-glucoside being the most abundant anthocyanins, each of which accounted for about 32% of the total anthocyanins. Flavanols ranged from 0.016 to 1.674 mg g-1 FW with procyanidin B1 being the most abundant compound, which accounted for 50% of the total variation in the group. Quercetin 3-O-glucuronide and quercetin 3-O-glucoside were the most abundant compounds in the group of flavonols whose contents ranged from 0.001 to 0.176 mg g -1 FW. For the group of hydroxycinnamic acids, the content ranged from 0.006 to 0.822 mg g-1 FW, with caftaric acid being the most abundant compound and accounting for 73.7% of the total variation. In general, wine grapes had higher concentrations than table grapes for all of these compounds except for hydroxycinnamic acids for which no significant differences were found between wine and table grapes. Berry colors affected the total contents of anthocyanins, but had no apparent impacts on other groups of compounds. The relative abundances of these five groups of compounds are in the order of anthocyanins, flavanols, flavonols, hydroxycinnamic acids, and hydroxybenzoic acids which explained 52.1%, 23.3%, 5%, 17.6% and 2% of the total phenolic variation, respectively. Positive correlations (0.151-0.535) were found among these groups of compounds. As expected, these groups of compounds wer all negatively correlated with berry weight. From these analyses, several cultivars with high contents of total and individual polyphenols were identified.